Turbine rotors and compressor rotors include individually removable blades that are conventionally mounted in a peripheral array of individually manufactured blades in interlocking slots in the rotor disc that match the blade roots. High rotational speeds require that the blades be securely mounted and blades are exposed to high temperature variations during operations as well as axial loading from flow of gas over the air foiled and platform surfaces. Individual blades are periodically removed during repairs and inspection. Preferably any blade locking mechanism is installed and rapidly removed with no damage to the rotor hub and blade root.
Many different types of locking devices are provided in the prior art. One low cost method of retaining small blades is with counter sunken rivets, which extend through the slot. The riveting operation on the bladed disk assembly is unreliable and frequently requires rework. Riveting machines are relatively expensive and limit the location where the work can be performed. Inconsistent load is applied by the crushed rivet and therefore the radial load on the blade varies depending on the installation.
Even when complex blade root locking systems are used, at times the blades loosen during grinding of the blade tips thereby creating variations in the outer rotor assembly diameter. Since blade tip clearance is of critical importance in maintaining the efficiency of the engine, variation in the outer rotor assembly diameter is undesirable.
As well, rivets have been known to develop insufficient axial resistance to the axial loads imparted on the blades and allow the blades to slide within the slots in the rotor and thereafter rub against adjacent components causing contact damage.
Many of the blade retention systems of the prior art involve relatively complex and expensive interlocking components that are not readily removed during repair operations. Some systems provide a resilient radial outward force that is variable and do not adequately support the blade roots radially during grinding of the blade tips.
It is an object of the present invention to provide a simple inexpensive blade retention scheme that adequately supports the blade during grinding operations of the blade tip.
It is a further object of the invention to provide a retention scheme that supports the blade with sufficient radial load to grind the rotor assembly without use of complex tooling or the need for high speed grinding.
Further objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below.